JP7232198B2 - System for monitoring physiological parameters in cardiopulmonary bypass - Google Patents

Description

The present invention relates to an integrated system for monitoring physiological variables in a heart-lung machine, particularly using a pressure transducer intended to act directly on the heart-lung machine.

Cardiopulmonary bypass (also called CPB) is currently the most commonly used technique in heart surgery. With this technique, a slowed cardiac arrest state can be achieved so that circulation and pulmonary ventilatory support to the patient can be facilitated to assist the surgeon in performing different cardiac procedures. Blood flow is maintained by a mechanical pump imaged into the heart-lung machine. A heart-lung machine is fairly complex and includes, along with a pump, several devices necessary to maintain the blood flow and oxygen needed to keep the patient alive during surgery. That is, oxygenators, arterial lines, arterial filters, and the like. Cardiopulmonary bypass is a high-risk procedure that requires careful monitoring of the patient's physiological parameters.

The Standards and Guidelines for Perfusion Practice of the American Society of ExtraCorporeal Technology strongly recommend that pressure and temperature measurements be taken at multiple points on the heart-lung machine. However, currently available pressure and temperature monitors and transducers are intended to monitor patient vital signs, which are parameters that differ significantly from the pressure and temperature signals in a heart-lung machine.

The table below shows the typical value ranges within which the patient monitor operates and the value ranges required for monitoring during cardiopulmonary bypass.

Thus, in addition to the insufficient value range, the use of commercially available sensors presents a fundamental problem. That is, the sensor is designed for monitoring patient pressure and temperature, not for a heart-lung machine. For example, in the case of pressure transducers, there are two commercially available types.

A mechanical pressure transducer (also called a pressure isolator) is a dome divided into two compartments with a connector on each side and a flexible membrane separating the two compartments. This type of transducer should be connected to the arterial line of the CPB circuit through a luer connector and be fluid filled on the side connected to the arterial line. The other side is filled with air and connected to a mercury or aneroid type pressure gauge. This type of converter has many drawbacks. The first drawback is that it is difficult to assemble. That is, one side of the membrane must be filled with saline and the membrane must be properly positioned. Failure to do so may result in imperfect pressure measurements. A second drawback is that due to the high pressure, blood often enters the dome. This can cause clotting and can disrupt pressure measurements. A third drawback is attenuation of pressure waves. This is due to the nature of the device, which can only measure the average pressure in the circuit, which, like roller pumps, can lead to erroneous measurement results. For example, there are often pressure peaks that cannot be identified in this type of system. This type of converter also has additional drawbacks.

A second type of pressure transducer known in the market is the disposable electronic pressure transducer. This is the current state of the art for patient pressure monitoring. It consists of a dome with attached electronic sensors with cables. A cable is provided at one end with an electrical connector to be connected to an external pressure monitor. However, this transducer also has several drawbacks with respect to pressure measurement during CPB, as it is not specifically designed for monitoring pressure in the heart-lung machine. For example, the circuit in which the electronic pressure transducer is provided may also be provided with an extension line, a 3-way stopcock for nulling the monitor, a thrombus tubing set, and a flow device. The transducer is connected to the circuit through a non-compliant extension wire attached to the luer lock connector. The transducer circuit needs to be filled with saline so that pressure can be sent to the transducer. A further drawback concerns the flash device in which the converter is provided. The device should be connected to a saline bag pressurized at 300 mm Hg to prevent backflow of blood into the transducer wires. However, it is not uncommon for the internal pressure of the CPB circuit to exceed 300 mmHg, which causes backflow of blood in the line and subsequent clotting, making pressure monitoring difficult. Additionally, the function of the flush device is to maintain a 3 mL/hr water flow through the transducer circuit to prevent blood clotting at the circuit end. This flow is achieved by a pressure gradient between patient pressure (typically 120/80 mmHg) and 300 mmHg due to the pressure bag. However, during cardiopulmonary bypass, even if the pressure does not exceed 300 mmHg, the pressure gradient drops significantly, and if there is no flow in the circuit, coagulation can occur without regurgitation. A further drawback with electronic pressure transducers used in CPB is that there is a liquid column between the transducer and the point of measurement because the transducer is connected to the CPB circuit via a serum-filled pathway. For patient pressure monitoring, the transducer should be level with the patient's mid-axillary line to counteract the effect of the liquid column on the measured pressure values. However, there is no reference point in the CPB circuit and the atmospheric pressure itself is the reference. Since the measurement points can differ in height from each other, the pressure measurement evaluation must also take into account the height difference between the measurement point and the transducer fixing point. Otherwise the measurements may be misinterpreted.

Additionally, temperature sensors are also used during CPB procedures. It is often reusable and cannot be placed in direct blood contact within the CPB circuit. Therefore, typically a disposable adapter is used to thermally connect the reusable sensor to the blood at the point of measurement. Not only are such adapters difficult to obtain on the market, the thermal connection between the sensor and the adapter can cause measurement errors. Additionally, temperature sensors are often less tolerant and can introduce measurement errors as they are used.

SUMMARY OF THE INVENTION To overcome the aforementioned drawbacks, an integrated system for monitoring physiological variables in a cardiopulmonary bypass (CPB) procedure is provided.

The system according to the invention comprises three basic components. Specifically, a disposable CPB transducer, a mini-monitor , and any central monitor connectable to the mini-monitor . The CPB transducer can be manufactured in three types. A pressure-only transducer, a pressure and temperature transducer, and a temperature-only transducer.

The integrated system of the present invention for monitoring physiological variables in a cardiopulmonary bypass (CPB) procedure will be better understood with reference to the accompanying drawings. The figures are exemplary only, and those skilled in the art will appreciate that several additional embodiments may be implemented without departing from the scope and concept of the invention described below. The figure is shown below.
1 is a schematic diagram of a CPB pressure transducer in accordance with the system assembly of the present invention; FIG. FIG. 2 is an electrical diagram showing a CPB pressure transducer in accordance with the system assembly of the present invention; FIG. 3 is an electrical diagram of a second embodiment showing a CPB pressure and temperature transducer in accordance with the system assembly of the present invention; FIG. 4 is an electrical diagram showing a third embodiment of a CPB temperature transducer according to the system assembly of the invention. 5A and 5B are schematic views of the mini-monitor of the system assembly of the present invention viewed from the left, front, right and back respectively. FIG. 6 is a schematic diagram showing a compact central module of the system body of the invention. FIG. 7 is a schematic diagram showing another control module and video monitor assembly of the system assembly of the present invention;

As shown in FIG. 1, a minimal system according to the invention for monitoring physiological parameters in a heart-lung machine basically comprises two components. That is, the CPB transducer (110) shown in Figure 1 has a sensor compartment (80), a connecting cable (20), an electrical connector (10), a housing (90), and optional fittings (100). . A housing (90) is available in some instruments to allow connection to some tubular instruments present in the CPB circuit. The joint (100) is for fixing the assembly behind the mini-monitor (30) as shown in FIG.

FIG. 2 shows the electrical configuration of the CPUCPB converter (10). A disposable pressure sensor (51) is provided within the sensor compartment (80) and is in direct contact (50) with the patient's blood through a hole in the housing (90). The disposable pressure sensor (51) is connected by a cable set (20) to the electrical connector (10) of the CPB transducer (110). Therefore, it is possible to directly measure the pressure in the CPB circuit.

Due to this configuration, the system according to the invention for monitoring the physiological parameters of a heart-lung machine offers a number of advantages over the prior art. Highlighted ones are listed below.

• Extremely simple to assemble as the pipe is cut at the point where the pressure is to be measured and the CPB transducer (110) is inserted in place.

• No preprocessing is required for the converter as it is inserted directly into the CPB circuit itself.

• Blood flows continuously through the transducer without stagnation points or obstructions, so there is no risk of coagulation within the transducer.

・Since there is no liquid column between the transducer and the measuring point, there is no need to adjust the height of the pressure transducer.

• Direct electrical connection to the pressure monitor reduces measurement errors due to noise and electrical interference in the transducer signal.

• Real-time measurement without attenuation.

• At the point of measurement, the actual pressure is measured, since the atmospheric pressure is referenced.

• Lower cost than conventional transducers, as no additional components such as valves, flushing devices, pressure lines, thrombus tubing, pressure bags, etc. are required.

In another embodiment shown in FIG. 3, the CPB transducer (110) may further comprise a disposable temperature sensor (52). With its insertion, the system according to the invention for monitoring physiological parameters of cardiopulmonary bypass also enables:

・Real-time temperature measurement at the measurement point without an adapter.

• Low error, high measurement speed without errors and delays due to thermal coupling due to the sensor being in direct contact with the blood in the circuit.

• Efficiency and convenience with pressure and temperature signals on the same connector (10).

・By using a new sensor for each operation, measurement accuracy is increased and reliability is improved.

・Since two sensors are embedded in the same housing, only one cable and one electrical connector are required, resulting in low cost.

In yet another embodiment, the CPB transducer (110) may have only a temperature sensor (52) for procedures requiring only temperature measurement and control.

It should be noted that in the three embodiments shown in FIGS. 2, 3 and 4, the CPB converter (110) of the system of the present invention uses the same electrical connector (10) to provide flexibility and compatibility for the overall system. performance improvement is guaranteed.

As mentioned above, the only pressure and temperature monitors available in the operating room are usually vital signs monitors used by anesthesiologists. Not only are the pressure and temperature channels dedicated to patient parameters, but as noted above, this monitor falls short of the pressure and temperature monitoring range required in CPB.

To overcome this problem and provide a simple, low-cost means for the extracorporeal cardiologist to monitor pressure and temperature during CPB, a system of the present invention for monitoring physiological parameters in a cardiopulmonary bypass is used for CPB. A pressure and temperature mini-monitor (30) is provided that is directly coupled to the transducer (110). This provides continuous measurement of the average pressure and temperature circuits without the need for additional auxiliaries.

The mini-monitor (30) shown in Figures 5A to 5D includes analog electronics that amplify and filter the pressure and temperature signals from the disposable sensors and digitize and process the analog signals for subsequent display (1) on the instrument panel. and a CPU to process for digital transmission to an optional external monitor (not shown). This mini-monitor (30) is compatible with the above three types of CPB transducers (110): pressure, pressure and temperature, and temperature, respectively, shown in FIGS. Additionally, the mini-monitor (30) is compatible with conventional pressure transducers. Moreover, the mini-monitor (30) does not require any kind of configuration. Simply connect a CPB transducer (110) or a conventional pressure transducer to the mini-monitor (30) and it will display values depending on the sensors available: pressure only, pressure and temperature, or temperature only.

Additionally, the mini-monitor (30) can be powered by an external power source or battery. Alternatively, when connected to an external monitor (not shown), power can be supplied via a digital communication cable, eliminating the need for an external power supply.

Structurally, the mini-monitor (30) comprises a display (1) for displaying pressure and/or temperature values and a user interface, and an electrical connector (2) for the CPB transducer (110), optionally with ease of placement. may have an extension line for sturdiness. The mini-monitor (30) has a rotary joint (3) on the back side for direct connection to the CPB transducer (110) or circuit tubing, and an auxiliary clamp joint (4). The mini-monitor (30) also has a connector (5) for external power supply and a connector for the communication cable to the central monitor.

The mini-monitor (30) according to the present invention has the following preferred technical features. Continuous monitoring of mean pressure in value range -400 to +999 mmHg, continuous monitoring of mean temperature in value range -20 to +50 °C, barograph for displaying instantaneous pressure changes, visual and acoustic for pressure and temperature Fittings for direct connection to static alarms, CPB transducers (10) or auxiliary fittings.

Moreover, the mini-monitor (30) can be electrically connected directly to the CPB converter (110) without intermediate cables. This improves the signal-to-noise ratio and reduces signal interference, thereby improving the quality and reliability of the signal from the transducer. Therefore, the accuracy of pressure and temperature measurements is also improved. It also includes an autozero system, as shown in another patent of the same assignee. This eliminates the need to zero the pressure transducer and allows the transducer to be connected directly to the CPB circuit. In addition to extremely simple operation, monitoring starts immediately by connecting an external power supply or inserting batteries and turning on the mini monitor (30).

As noted above, in many cases the pressure and temperature mini-monitor (30) meets the needs of the extracorporeal cardiologist, but it is not recommended for ECMO procedures, surgeries in which pumps provide pulsatile flow, or longer and more complex procedures. Additional information or resources may be required in certain situations, such as surgery. pressure curves, systolic and diastolic pressure values, hydraulic resistance calculations, trend charts, alarms, etc. To accommodate this particular situation, the mini-monitor (30) is provided with a connector for digital communication. Via this the systolic, diastolic and mean pressure and temperature values are sent to the external monitor (40) shown in FIG. This external monitor (40) on the other hand receives data from multiple mini monitors (30, 30', 30'', 30''') and
display as graphics and numbers in conjunction with each other. There are also some calculation functions. For example, it is a hydraulic resistance calculation as described later. It also has other features in common with commercially available vital sign monitors. visual, audible alarms, and the like.

According to the system according to the present invention for monitoring physiological parameters in cardiopulmonary bypass, the external monitor (40), when connected to the mini-monitor (30), in addition to receiving data for screen display, It also provides the power it needs to operate without an external power supply or battery. The external monitor (40) may consist of a single compact unit containing a CPU and a user interface. Alternatively, it may consist of a module containing a CPU and a user interface control panel, and an external video monitor connected via a video cable for more flexible placement in the operating room and improved user convenience. .

Importantly, the use of the external monitor (40) is not limited to pressure and temperature transducers, other sensors such as on-line flow and oxygen sensors, or other sensors compatible with the communication protocol of the external monitor (40). May be used with equipment.

Structurally, a compact external monitor (40) according to the invention may have a screen (41) and control buttons (42) for interaction with software. It also has a connector (43) and a digital communication cable (44) for connection with the connector (45) of the mini monitor (30).

Alternatively, a system according to the present invention may have a control module (60) and video monitor (70) assembly as shown in FIG. In this case, the central monitor (40) shown in Figure 6 is replaced by an external video monitor unit (70) connected via a video cable ( 120 ) to the control module (60). The control module (60) has control buttons (not shown) for interaction with the software of the remote monitor (70).

Some advantages of the system of the present invention over conventional vital signs monitors are as follows.

Improved signal quality

Conventional monitors have analog electronics that amplify and condition vital signs within the device and typically receive sensor signals through long cables. The signal from the sensor has a very small amplitude on the order of millivolts. Therefore, the quality and amplitude degrade when transmitted over long cables, which are typically present in interference-ridden environments. In addition, analog electronics are close to power supplies and CPUs, which are major sources of electromagnetic interference. All of this requires sophisticated signal amplification and filtering circuits to capture the original signal in the monitor. In the case of the mini-monitor (30) according to the invention, the pressure and temperature CPB transducer (10) is directly connected to the amplification circuit and the power supply is external. This results in an interference-free, loss-free and therefore higher-quality signal at the analog electronic circuit input. This results in simpler amplification and filtering circuits without compromising signal quality. In addition, the mini-monitor (30) digitizes and processes the signals, presents them on the built-in display and, after appropriate processing, the pressure and temperature values as digital signals with virtually no loss on the external monitor (40). It has a sending CPU. Therefore, the external monitor (40) simply displays the values processed by the mini-monitor (30), eliminating the need for analog electronics of any kind. Also, since the signal sent to the remote monitor (70) over the communication cable (80) is a digital signal, it is substantially immune to interference. All of this results in a system that is simpler, less costly, and yet more powerful than current monitors.

Simplicity and robustness

The system's design allows the use of extremely simple electronic circuitry, while improving the performance of commercially available systems. Plus, being simpler makes it more robust and less flawed.

modular

As mentioned above, the system is completely modular and can be scaled to meet user needs by simply adding new modules.

Flexibility

The system can be tailored to the requirements of each user or occasion. For simple surgery, the user may select only the CPB transducer (10) and mini-monitor (30). For more complex surgeries and procedures such as ECMO, each mini-monitor (30) and multiple CPB transducers (10) coupled to an external monitor (40) may be used. This allows all parameters to be viewed and controlled in addition to alarms and other features. Additionally, in the case of cardiac surgery, for example, a control module (60) + video monitor (70) system allows the control module (60) to be placed near the cardiologist. This makes the movement easier and ergonomically reasonable. The video monitor (70) can be placed high enough to be visible to other medical professionals in the operating room. Use a compact external monitor (40) that can be placed near the center console for increased mobility and ergonomics for ECMO, where the CPB works alone most of the time You may

practicality

The system is extremely easy to use. Simply mount the CPB converters (10) on the heart-lung machine, connect a mini-monitor (30) to each CPB converter (10), and connect the mini-monitors (30) to the central monitor (40) via a communication cable (44). for full monitoring. No additional steps are required as the system automatically monitors the circuit parameters just by turning on the instrument. There is no need to zero the converter or adjust the level.

Hydraulic resistance calculation

Hydraulic resistance calculations can be extremely useful in situations where it is desirable to assess resistance changes in a heart-lung machine during a procedure. For example, monitoring hydraulic resistance can verify normal operation of an arterial filter or oxygenator. Two pressure transducers and one flow transducer are required to calculate the hydraulic resistance of the system. Transducers must be installed before and after the device respectively to be evaluated, and flow sensors must be installed adjacent to the device and in the same series. The hydraulic resistance of the device is calculated by the following formula.
Rh = (Pe-Ps)/flow

During the ceremony,

Rh is hydraulic resistance,

Pe is the pressure at the device inlet;

Ps is the pressure at the device exit,

Flow is the total flow rate in the device.

Verification of device operation is usually accomplished by evaluating pressure and flow separately. However, this evaluation is complicated and the user is required to have extremely deep knowledge and experience. On the other hand, the analysis of fluid resistance is simpler and easier to understand. That is, the contributions of all other parameters are reduced to one value. Sensitivity and reliability are therefore greatly improved and the parameters are easier to interpret. That is, the resistance should be constant during treatment. A beginning increase in resistance may indicate a clog or clot within the device. A decrease in resistance may indicate a leak in the device. Furthermore, by using multiple transducers at appropriate points along the circuit (e.g., pre-oxygenator, post-oxygenator, post-arterial filter, etc.), when changing CPB parameters, you can see which device is having the problem.

Low price

Having fewer components and simpler circuitry, the system according to the invention is less costly.

Claims (9)

It comprises at least two components: a cardiopulmonary bypass (CPB) converter (110) and a mini-monitor (30), said CPB converter (110) being a compartment for a CPB sensor (80), said CPB sensor ( 80 ) with at least one disposable pressure sensor (51) in direct contact with the patient's blood through a hole in the CPB housing (90); a connecting cable (20); Having one electrical connector (10), one said CPB housing (90) and one optional fitting (100), said mini-monitor (30) is a direct connection to said CPB transducer (110). electrical connections and analog electronics for amplifying and filtering the pressure and temperature signals from the disposable pressure sensor, the CPU of the mini-monitor (30) for later viewing on the display. Digitizing and processing analog signals for digital transmission to an external display, said mini-monitor (30) further includes an auto-zero system to zero the pressure transducers and to calibrate said CPB transducers (110) . A system for monitoring physiological parameters in CPB, characterized in that it allows direct connection to the CPB circuit. The system of claim 1, wherein said CPB transducer (110) further comprises a disposable temperature sensor (52). 3. System according to claim 1 or 2, characterized in that the CPB converters (110) use the same electrical connector (10). Said mini-monitor (30) includes a display (1) for viewing pressure and/or temperature values and a user interface, an electrical connector (2) for connection to said CPB converter (110), and said CPB converter (110). ) or circuit tube, an auxiliary clamping joint (4), a connector (5) to an external power source, and a connector (6) for a communication cable to an external monitor. 2. The system of claim 1, wherein the CPB converter (110) is directly connected to the mini-monitor (30). Alternatively, the system can receive data from various mini-monitors (30, 30', 30'', 30''') and display the data graphically, numerically, simultaneously on the same display, and several 2. System according to claim 1, characterized in that it comprises an external monitor (40) capable of calculating: The external monitor (40) is compact and includes a display (41) and control buttons (42) for interaction with software, a connector (43) for a digital communication cable (44) and the mini monitor (30). 6. System according to claim 5, characterized in that it comprises a connector (45) for connection to a 2. The system of claim 1, wherein the system alternatively comprises a control module (60) and a video monitor (70) assembly interconnected via a video cable (120). 2. The system of claim 1, wherein the CPB housing (90) has a joint (100) for securing the assembly to a suitable support. The mini-monitor (30)
continuously monitoring mean pressure in the range of -400 to +999 mmHg;
continuously monitoring the temperature in the range of −20 to +50 ° C. , and
2. The system of claim 1, comprising having a fitting that couples directly to the CPB transducer (10) or auxiliary clamp.

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